#include <Adafruit_NeoPixel.h>

#define LED_PIN    1
#define LED_COUNT  15

Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

// Twinkle parameters
const uint8_t FULL = 255;
const uint8_t MIN_TWINKLE = 50; // how dim a twinkle can go
const int MAX_TWINKLE_TIME = 1000; // max ms per twinkle (was 2000)
const int MIN_TWINKLE_TIME = 250;  // min ms per twinkle (was 500)

// Track which LEDs are twinkling
bool twinkling[LED_COUNT];
int twinkleStart[LED_COUNT];
int twinkleDuration[LED_COUNT];
int twinkleDirection[LED_COUNT]; // -1 fade down, 1 fade up

void setup() {
  strip.begin();
  strip.setBrightness(255);

  // Start all LEDs full white
  for (int i = 0; i < LED_COUNT; i++) {
    strip.setPixelColor(i, FULL, FULL, FULL);
    twinkling[i] = false;
  }
  strip.show();
}

void loop() {
  unsigned long now = millis();

  // Start new twinkles randomly
  for (int i = 0; i < LED_COUNT; i++) {
    if (!twinkling[i] && random(1000) < 10) { // ~1% chance per frame
      twinkling[i] = true;
      twinkleStart[i] = now;
      twinkleDuration[i] = random(MIN_TWINKLE_TIME, MAX_TWINKLE_TIME);
      twinkleDirection[i] = -1; // start fading down
    }
  }

  // Update LEDs
  for (int i = 0; i < LED_COUNT; i++) {
    if (twinkling[i]) {
      float t = (float)(now - twinkleStart[i]) / twinkleDuration[i];
      if (t >= 1.0) {
        // Reverse direction
        twinkleDirection[i] *= -1;
        twinkleStart[i] = now;
        t = 0;
      }

      uint8_t brightness;
      if (twinkleDirection[i] == -1) {
        brightness = FULL - (uint8_t)((FULL - MIN_TWINKLE) * t);
      } else {
        brightness = MIN_TWINKLE + (uint8_t)((FULL - MIN_TWINKLE) * t);
      }

      strip.setPixelColor(i, brightness, brightness, brightness);

      // Stop twinkle if fade back complete
      if (twinkleDirection[i] == 1 && t >= 0.95) {
        twinkling[i] = false;
        strip.setPixelColor(i, FULL, FULL, FULL);
      }
    }
  }

  strip.show();
  delay(15); // faster frame rate (was 20)
}